According to IMDb trivia, Culkin developed a scar on his finger while filming the 1990 movie after Pesci bit him during a scene.
The ‘Home Alone’ Moment Macaulay Culkin Still Carries With Him
The injury happened while Culkin and Joe Pesci were rehearsing one of Harry’s confrontations with Kevin. Pesci’s character threatens to bite Kevin’s fingers off one by one, and during the rehearsal, the actor bit Culkin’s finger. The incident left Culkin with a small, permanent scar.
Source: IMDb
Culkin was only nine years old when the accident happened. Years later, he recalled the moment and described seeing a look of genuine panic on Pesci’s face immediately after the bite, thathad not been planned as part of the scene.
The sequence was part of the film’s many physical confrontations between Kevin and the two burglars. Harry and Marv spend much of the movie falling victim to Kevin’s elaborate traps, with the production relying on stunt performers for some of the more dangerous gags.
The incident also became one of the more unusual behind-the-scenes stories attached to the Christmas classic. Culkin’s finger injury never appears as part of Kevin’s story, but the scar has remained with the actor as a permanent connection to one of his most famous roles.
